The Effects of Early
Social Disruption on
Brain and Behavioral Development

The
Network has conducted several related studies in Rhesus monkeys that
address how early social deprivation affects brain and behavioral
development. Monkeys who were removed from their mothers at either 1
week of age or 4 weeks of age developed strikingly abnormal behaviors
compared both to each other and to normal monkeys who left their
mothers at 6 months, the usual time for maternal separation.
Neuroanatomical studies of these monkeys have shown distinct
differences in some areas related to social functioning. Other studies
involve introducing monkeys separated at 1 week of age (who appear to
lack any social drive after the separation) to a
“supermom” (a female monkey known to adopt
infants). These studies are showing that, while the behavioral
abnormalities seen in these separated monkeys can be remediated by the
introduction of a substitute mother, there appears to be a narrow
window of opportunity for the reintroduction of maternal care. After
this window of opportunity, it is highly unlikely that either the
infant or the mother will be amenable to
“adoption.”

The
behavioral abnormalities seen in the 1-week and 4-week separated
monkeys appear to have long-lasting consequences. The first separated
monkeys are now of reproductive age, and several have had infants of
their own. Those monkeys separated from their mothers at one week of
age display highly abnormal parenting behaviors. We are watching the
infants of these mothers closely to see if there is any
intergenerational transmission of the abnormal behavioral profile.

Another
study that involved re-organizing separated monkeys into unfamiliar
social groups has just been concluded, and behavioral data show
striking behavioral abnormalities among the one-week- and
four-week-separated monkeys. This suggests that there may be some
further brain and behavioral abnormalities caused by the early
deprivation that do not manifest themselves until later in life, or
until the introduction of some social stress (perhaps akin to the
social stress undergone by adolescents entering a new school setting).